import java.util.Scanner;

public class AlphaFilter {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        System.out.println("请输入一个字符串：");
        String input = scanner.nextLine();
        
        String result = input.replaceAll("[^a-zA-Z]", "");
        
        System.out.println("只包含字母的字符串是：" + result);

        scanner.close();
    }
}
